The Impossible Girl
by HopelesslyClueless92
Summary: A strange woman shows up at Hogwarts with a secret. A secret that could very well unhinge and unravel the powers of the Dark Lord...Tom Riddle/OC R&R.
1. Chapter One

_Hi everyone! So this is my first Harry Potter Fanfic so bear with me please! I hope you enjoy this first little chapter and I would greatly appreciate it some feedback._

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Prologue

She ran. Ran as fast as she could through the dark corridors, towards the Great Hall, knowing what was coming and for the first time in her life, felt truly, truly scared.

She quickened her pace as she past the lifeless bodies on the floor, refusing to look. Was this all somehow her fault? If she didn't leave all those years ago, would the future not be somehow different? Would she not be sitting at home, right at this moment, two or three children at her feet, her husband looking at her adoringly? She pushed those thoughts aside. Too many nights she had spent wondering 'what if'. During her last few moments, she would not think of that. Instead she would think of what she was saving. That was all that mattered.

Finally, she burst into the Great Hall, all eyes on her and as she strode forward, she let her wand slip through her fingers.

She never gave much thought as to how she would die, considering it was near impossible. But then all must die and, honestly, dying in the place of someone she treasured? She shrugged to herself as she looked at into the eyes of the man she loved. To the impossible girl, it seemed like a pretty good way to go.

"Do it. Kill me."

* * *

She sat, crossing and uncrossing her legs, twirling her wand between her fingers, an eyebrow raised at the man sitting across the mahogany desk from her. She finally let a long breath out and leaned forward, placing her elbows on the table.

"You're asking for a lot here, Dumbledore."

The headmaster of Hogwarts School of Witchcraft and Wizardry, smiled at her, a seemingly innocent smile; she knew better.

"I asked you one question, Miss Andrews."

"One question that has a thousand different meanings to it." She sighed, "I told you, after the last time, I wouldn't come back…how easily I succumb to your charms, old man."

He laughed, his half-moon glasses sliding down his nose even further.

"This is a slightly different request than the other two times- before I asked you to be a student. This time I'm asking you to teach."

"Yes. Physical education." She drawled the two words out in distain. "I'm sure the pure-blood families will love to learn that their children have to take part in such a Muggle topic."

"Physical fitness is a problem here at Hogwarts, and who better to ask than a woman who uses her body on a daily basis?"

The girl snorted. "To kill _monsters_, Dumbledore. I'm also not too sure they'd be overly happy letting their kids spend the year with me. You know how the general public take me."

"I always thought you were much loved."

She raised both eyebrows at this comment.

"Well you always were at this school."

"Yes that's because half of the school's population, is male. And I'm, well…_me_."

He laughed again. "That you are."

The girl suddenly narrowed her eyes on the elderly man opposite her.

"Let's cut to the chase here. I'm going to guess you asked me to do this job for two different reasons. Number one: The Ministry has asked you to keep an eye on me because apparently I'm not being inconspicuous enough. Reason number two: Harry Potter."

Dumbledore leaned back in his chair and studied her with a gaze of slight bemusement.

"Impressive, Miss Andrews. I will not lie to you, you are indeed correct. Concerning your first answer, you must agree with them a little. You know how serious this is. You _must_ stay out of the public eye. Remember, you are meant to be _dead_."

The girl sighed. "I know, I know. Then what's the point having me here? Isn't there a Malfoy in Potter's year? You might as well stick a massive sign above my head saying, 'Only joking! Sorry you turned into a crazy psychopath but I'm actually not dead! Please become sane again!' Doesn't sound like keeping a low profile, does it?"

Dumbledore gave her a stern look before saying, "You will not need to worry about Mr Malfoy. A new teacher is not something he will care about very much."

"I beg to differ. Sure, any normal teacher, maybe. But the Hunter? The strongest woman in the world, a power more deadly than a giant? The only person in the entire universe who cannot be harmed by a wand?" She set her mouth into a tight line. "Yes, you're quite right Dumbledore; he's not going to report back to his father about me, _at all_. And encase you haven't noticed, Dumbledore, I don't age. You don't think Potter is going to recognise me from all those times I saved his life?"

"Then you know must you must do."

"Like hell am I going undercover again. _Like hell_."

Dumbledore sighed. "I didn't want to have to play this card but…" He let out another long-winded sigh and the girl could already tell where this was headed, "You promised your best friends you would look after their son…not to mention the unbreakable vow you made with-"

"Don't." She flinched away from him like he had cursed her. He didn't like being cruel, but desperate times called for desperate measures and as things stood as they did, times was never more desperate.

He waited a moment before she raised her head and gave him a nod. "Fine, I'll do it." She drew a deep breath. "But don't ask me how this is going to work, Dumbledore. I can't just fall in love with whoever I want. It has to be natural. And he's…well…you know…his godson. It feels morally wrong."

"You knew from 1981 that this day would come. And here it finally is. I know you won't let them down, Sarah."

He moved to get up and she followed the notion. As she made her way to the door, he smiled at her once more.

"You know where your classroom and your rooms are so you have two days before term starts to get yourself reacquainted with the school." He gave her an overwhelmingly sad smile. "I _am_ sorry, Miss Andrews."

She nodded but didn't say anything, she didn't trust herself to. Giving him a weak smile, she made her way back down the corridors and ran into her dormitory so she could have a good, long, well-deserved cry.

* * *

_She was standing in the middle of the Great Hall. The sky above her was dark and ominous looking. She wasn't alone._

"_I am so sorry." The words came out as helpless as ever and he probably didn't care one bit._

"_You left me. And you think a sorry is going to make everything better? You idiotic, little girl. You never learn, do you? This is your entire fault, all of it. All of the pain and suffering. Not by mine hand but by yours."_

_He pointed her wand at her and smirked._

"_Sweet dreams, my love."_

_She screamed._

Sarah Andrews gave a yelp and tumbled off her bed, landing on the floor in a heap of pillows and blankets. She grimaced and quickly got up, rearranging her bed as she went.

Damn it. She thought those dreams had stopped. But ever since what happen at the Ministry of Magic over the summer, they had started again. She felt a tear fall. She should have been there. She should have saved him. She should have saved Sirius.

She had done her crying, had done her descent into madness. It had taken all of her will but she managed to pick up the pieces of her shattered life for the third time in her extremely long existence and carry on. She had no other choice. There was a world that needed saving. And she was destined to be that saviour from the day she was born.

She gave a growl of frustration and hit the wall, ignoring the crack that appeared when she did so. That was not fair! She should be out on the streets of London! Saving lives, not in here, protecting Lily and James's son. But he was 'the boy who lived' and she did promise to protect him and when the time came-

No. She would not think of such things. There were more pressing matters to take care of. Like how she should change her appearance.

Sarah briskly marched into the bathroom and looked at herself in the mirror. Every hunter that had ever lived was something akin to a Greek goddess. This was simply bait for the monsters they hunted; and it worked extremely well.

She herself had rich brown locks that flowed down to her waist and deep green eyes that seemed endless, never-ending. They were those types of eyes that when looking at someone, they looked like they were looking into that person's soul. And now, thanks to Dumbledore and her stupid unbreakable vow, she had to change herself.

After thinking about it for a split second, she muttered an incantation under her breath and flicked her wand around her face. When she looked in the mirror once more, she gave a shrug of acceptance.

Instead of her brown locks, her hair was light blonde and was cut into a smart bob. Her eyes were a chocolate brown, so much less revealing that her original eye colour. Her face was a little rounder and her lips slightly smaller. It would have to do. Even though she looked kind of like a virgin primary school teacher.

She turned and with another flick of her wand, all her clothes and belongings sorted themselves out and she rushed over, grabbing a pair of jeans and a blue hoodie and throwing them on. Giving a swift look around the room and seeing everything was in order, she decided to it high time to get a look around the castle again and marched out the door.

Fifteen minutes later and she realised that the castle had not changed one bit. Nearly everything was exactly the same. _Well that was a complete waste of time…_

"Miss Andrews!"

She turned slowly on her heel to see Dumbledore striding up to her with a bat-like man following closely behind…oh God no…

Dumbledore gave a nod of approval at her new appearance. "Excellent. No one will suspect a thing."

She nodded before turning to Snape and glaring. "Severus. I would say it's good to see you again but we both know I would be lying."

He scowled at her. "My feelings are completely mutual Miss Andrews."

"I'm sure you've heard that I'll be staying here for a year. I would quite like it, knowing what you get up to in your spare-time and being the little double agent that you are, if you could keep your master out of your head and make sure he only knows that I'm a new teacher."

His scowl deepened; he clearly didn't like being ordered about, much least by a former classmate. Dumbledore gave an airy wave of his hand.

"I have already explained the details of our plan to Severus so fear not Miss Andrews." He smiled widely before continuing. "Now, we have some important things to discuss. I would like you to follow me to my office."

Once again she sat in front of Dumbledore's desk but this time she had no idea what for. Slowly he opened a cabinet and stood back so Sarah could see what was inside. It was a pensive.

"What are you doing, Dumbledore?" She asked wearily, getting out of her chair and edging towards the door.

"You know exactly what I'm doing, Miss Andrews. We need your memories. For when the time comes."

Sarah's head was reeling. Why couldn't she just tell Potter all that happened? Why would she have to show him?

"All of them?" She asked, already knowing the answer. Dumbledore nodded and Sarah let a groan of annoyance slip through her lips. She sighed and retrieving her wand, placed it to the side of her head and thought hard. Although she had taken memories from her head before, she was not prepared for them to go to the front of her mind. Every encounter, every touch, every kiss…it was like watching a movie of herself in high definition.

When she finished and had placed the memories in a jar, she quickly handed it to Dumbledore before falling to the floor, black spots dancing before her eyes. It was just too much information to handle and she felt extremely light headed. She could hear Dumbledore's urgent voice from far, far away but before she could even decipher what he was trying to say, everything suddenly went black.

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_There's the first chapter. I know it's confusing but it'll become clearer as time goes on. Please review and tell me what you think. Thanks!_


	2. Chapter Two

_Hey, hey! Thanks to everyone who's been reading and following! Enjoy this second chapter and please review!_

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_February 1942_

"Why in God's name did I think this would be a good idea? This is all your fault, Dumbledore!"

Sarah scowled at the man beside her as he turned to look at her incredulously.

"I simply asked you if you wanted to learn witchcraft. It was Professor _Dippet_ that accepted you." He made a slight tsking sound, watching in amusement as her left eye twitched. He always did know how to push her buttons, even when they were younger.

"Yes, well, now I'm thinking what a bad idea this was." She sighed before adding, "Why do I have to wait outside the doors? Why didn't I just arrive like any normal student?"

"Because Professor Dippet wants to introduce you to the school. It _is_ slightly unorthodox having a student become a fifth year, out of the blue. Professor Dippet wants to explain to the pupils what you are. We also need to sort you into a house. We discussed this already, Miss Andrews."

She glared. "Don't you, 'Miss Andrews' me; we're nearly the same age. And yes, that's a _brilliant_ idea. Let's make everyone know that there will be a new school freak from now on." She sighed. "I should have started in September. Not in bloody February."

Dumbledore gave her a small smile as they both heard thunderous applause from the Great Hall.

"We did offer you to join in September but I think your response was limited and vague. Something about a vampire gang in Romania."

Sarah's eyes suddenly lit up. "I remember that. It was quite a large gang and tough too. About fifteen of them, if I can recall correctly. That was fun…"

Dumbledore smiled at her as she adorned that far-away look in her eyes. He heard the doors creak, ready to open and both of them started. She threw him a frightened glance.

"Do not fear, the school will love you, Miss Andrews."

Sarah raised an eyebrow but said nothing, looking straight ahead and nodded determinedly.

She then heard Professor Dippet say something and the Great Hall doors swung open, revealing her to the whole school.

As she gave a timid smile to the extremely long four tables, she walked briskly beside Dumbledore, feeling completely humiliated. Eyes were burning holes into every part of her body as the pupils and staff attempted to drink the sight of their new student. As embarrassed as she was, Sarah resisted the urge to roll her eyes. _Yeah, yeah. It's just a damn face, people. You might not get used to it but be prepared to see it quite a lot._

Sometimes she disliked the way she looked. No one, apart from a very select few, tried to see past her features. No one tried to get to know the person underneath the strength and mystic. If she had to answer why she ever went to Hogwarts in the first place, it was probably for that reason. She really wanted some good, honest-to-God, true friends.

When she finally reached the top of the Great Hall, she turned swiftly on the spot and looked out at her fellow pupils. Professor Dippet appeared beside and gently put a hand on her shoulder.

"Hogwarts, I'd like to introduce our new student, Miss Sarah Andrews, who will be entering fifth form this term. I hope you all make her feel welcome." He turned to her, smiling. "Now, let's get you sorted, yes?"

She grimaced slightly but nodded all the same. Placing herself on the small tool in front of her, Professor Dumbledore carefully sat the hat on her head.

"_Hmmm….interesting…a Hunter at Hogwarts; never seen your kind here before. Well you have strengths that will do well in all of our houses."_

_Not in Slytherin_ Sarah thought dryly.

"_No?"_ The sorting hat asked casually, _"And why is that?"_

_Because I'm not a full-blood. I'm not really anything._

"_I beg to differ, Miss Andrews but if it's not Slytherin you wished to be placed into, better put you in…RAVENCLAW!"_

A thunderous applause roared through Great Hall as Sarah grinned and slid off the stool, handing the hat back to Professor Dumbledore. Giving Sarah a wink and gesturing to the Ravenclaw table, Dumbledore went back to his seat.

The moment she sat down, a girl with flowing black-hair and sparkling blue eyes smiled at her kindly.

"Hello, welcome to Hogwarts." She said, taking Sarah's hand and shaking it vigorously, "I'm Hollie McHart, one of the Ravenclaw perfects. I'm also in your year."

Sarah smiled back at her. "Nice to meet you."

"I can't believe the Hunter has come to Hogwarts! I thought you were a myth!"

Sarah laughed, feeling a bit more relaxed. At least _one_ person likes me; that's a start. "We don't exactly make our presence know a lot. We don't really do well with other people."

Hollie stared at her, mouth agape. "You're…very _pretty_."

Sarah resisted the urge to roll her eyes. "It's an invitational kind of thing. Attracts monsters to my kind. Every hunter who has ever existed looks like this."

Hollie nodded in awe. "You must have loads of boys after you. How lucky."

Sarah pulled a face as she placed some chicken onto her plate. "Not really. Like I said, I'm not the most sociable of people. I tend to blend into the shadows. I've never even had a boyfriend."

Hollie snorted. "Well, I can tell you one thing- you won't be blending into the shadows here. Every boy in his room has his eyes on you." She paused, turning her head towards the Slytherin table. "Well, not every boy."

Sarah followed her gaze and found herself staring at a black-haired boy about her age, with perfect pale, white skin and lovely cheekbones. He was quite beautiful in a mysterious kind of way; if Sarah had to pass comment and felt a little upset he wasn't looking at her. _Jeez, Andrews, you don't even know him._

"Who's he?" Sarah asked, trying (and failing) to sound indifferent.

Hollie smirked slightly. "His name's Tom Riddle, he's in our year, he's a prefect for Slytherin and the school heart-throb." She paused before looking at Sarah. "I'm sure you can see why."

The Hunter nodded slowly. "He is…very nice looking."

"Don't waste your time. He doesn't date. He never taken any interest in the girls here and let me tell you, our year has a plentiful supply of pretties."

"Pretties?" Sarah snorted, munching happily away at her chicken.

"You know, good-looking girls." She turned and pointed further down the Slytherin table to a very beautiful girl with long, blonde hair and blue eyes. "That's Olive Hornby. She's being chasing Tom Riddle since first year and he hasn't even batted an eyelid in her direction. I mean, she's a complete cow, but she's gorgeous. And a full-blood. They're perfect for each other."

Sarah scowled. "Well, if he's a massive purist, he's going to _hate_ me. I'm not really anything."

Hollie smiled at her. "Don't worry, Sarah. I'm sure the rest of school will love you. Nearly all the boys do already."

Sarah grinned at her before turning her gaze on Tom Riddle once more. Only this time, her eyes locked immediately with a pair of deep blue ones. And they looked completely furious.

"Woah, what did you do?" Hollie gasped, having noticed what happened.

Sarah tore her eyes away from his and whirled around back in her seat. "I dunno. As I said, maybe he doesn't like me because I'm not from a wizarding family." She shrugged slightly. "I honestly couldn't care less. It's not like I'm going to have to spend any time with him anyway."

* * *

"What do you mean, private lessons?!"

Sarah gaped at the headmaster of Hogwarts in outrage. Sure, it was going to be difficult for her to catch up with everyone else but she fought demons on a daily basis, she was pretty confident she could catch up on some measly school-work!

"You heard me, Miss Andrews. As you are joining fifth year and have never used a wand in your life, you will need training. OWLs are also this year so you need to be prepared. So we have hand-picked certain students in your year who are going to assist you." He gave her a small smile, "This also means you will meet more people. Isn't that nice?"

Sarah scowled. "Yeah, it's just _peachy_."

The headmaster, however, paid no heed to her sarcasm and quietly called in the students who would be helping her. Initially she beamed when she saw Hollie, who bounced into the office, grinning like a mad-woman. Her heart then plummeted when in walked Tom Riddle and Olive Hornby among one other student that she didn't know. _Great. The two biggest purists in the planet are going to be tutoring me. Bloody brilliant._

"Miss Andrews, may I introduce the two prefects for Slytherin; Mr Tom Riddle and Miss Olive Hornby."

Sarah decided it might as well suit to be nice. "Hello, nice to meet you."

Olive stung her nose up in the air and sneered. "Charmed, I'm _sure_."

_Snobbish cow._

Tom, in contrast, flashed a smile and bowed slightly. "A pleasure, Miss Andrews."

Sarah raised her eyebrows in surprise. _Maybe he's not so bad after all…_

Behind them Hollie was shooting daggers at Riddle and mouthing '_He's an asshole!' _to which Sarah burst out laughing.

"I assume you've met Miss McHart then?" Professor Dippet asked, throwing a stern glance at Hollie.

Sarah stifled her giggling and nodded at the Headmaster.

"The last person to introduce is one of the prefect's for Gryffindor; Miss Minerva McGonagall."

The girl glanced timidly at Sarah, who gave a wave and a polite smile in return.

"So, Miss McHart will be helping you with your studies in Charms and Herbology, Miss McGonagall will be tutoring you in Transfiguration, Miss Hornby will be helping you with History of Magic and Mr Riddle will be assisting you with Potions."

Sarah nodded while Hollie looked confused.

"Who's going to be helping her with Defence against the Dark Arts, Professor?"

At this both the Headmaster and the Hunter began chuckling lightly.

"I don't think that'll be a problem, Hollie." Sarah replied, "Since there's not a wand on this earth that can harm me and I'm pretty much invincible."

Hollie nodded her head in understanding. "Oh yeah, forgot about that."

"Maybe you should actually _listen_ when Professor Dippet is talking, McHart." Olive muttered.

"Was I asking you, snake?"

"_Ladies_." Dippet warned before turning back to Sarah.

"I assume when you get your timetables tomorrow, you will be able to converse and find out which evenings it's best to study with each of these students, yes?"

"I guess." She answered, looking to the other pupils who all nodded.

"Excellent." Dippet said, happily, "Now, if there's nothing else, you can all return to your common rooms."

And with that, the five students left the office.

The moment they got out into the deserted hallway, however, Olive pulled her wand out.

"So you immune to _any_ spell, right?"

Sarah turned to see Olive pointing a wand in her face and smirking. Hollie stepped forward.

"Don't be stupid, Hornby."

"I wasn't talking to you McHart so shut your trap."

Sarah looked blankly at the beautiful girl and nodded.

"That's right." She confirmed loftily. She already knew where this was headed.

"So even the _unforgivable curses_?"

"Olive, not only are you not allowed to use spells on students, the unforgivable curses are _illegal_."

"Stay out of this, teachers pet." Olive spat at Minerva.

"It's fine, Minerva." Sarah said softly to the Gryffindor before replying to the Slytherin. "Yes, even those."

She quickly glanced at Tom Riddle who was watching her with an unreadable expression. But something dark was swirling around in his eyes. He was looking at her almost like she was a prize or trophy. It unnerved her. However, Olive's whiny voice brought the Hunter back to the present.

"Well then, you won't mind if I give one a go and see what happens, do you?"

Sarah raised an eyebrow. _Enough of this_. "As much as I would _love_ to see you get expelled because clearly you have some grudge against me even though I barely know you, no, you cannot curse me because _nothing_ will happen. It's a waste of your time and energy and frankly I don't want to have to watch you being dragged off to Azkaban, okay?"

Olive's arm went slack and she gaped at the girl before her.

"Now, if you're quite finished, I want to get back to my common room, alright?"

Olive nodded mutely and put her wand away. "I'll talk to you tomorrow, Andrews." And turned on her heel before giving her a '_this isn't over look'_ to which Sarah pulled a face. Immature, yes but she was old enough to do that sort of thing and get away with it.

Minerva gave a sigh of relief and grinned at Sarah. "Thank God for that! I thought I was going to have to jinx her or something. Look, I'll come see you tomorrow, okay Sarah?"

Sarah grinned. "No problem, see you then!"

Minerva flashed her and Hollie a smile before sprinting off down the hallway.

"So…." Sarah turned her gaze on the remaining student, bar Hollie. "Tom, correct?"

"Tom is fine…or Mr Riddle if you prefer."

Sarah shot Hollie look to which she sent one back that screamed _told you so. _

"Considering you're younger than me, I'll go with Tom." She smiled but apparently he didn't seem to think that age was an important factor.

"While that may be true, Miss Andrews, you look the same age as myself." He eyed her critically before stating, "And considering your intellect is slightly below par, I would think I have the upper-hand when it comes to our _relationship_."

It was Sarah's turn to gape. _The nerve! Who did this guy think he was, talking to her like that? Did he have any idea who he was speaking to?_

"Listen here, _buddy_." Sarah barked, marching towards him so they were face to face, "I don't know who you think you are-"

"As we have already established, I'm Tom Riddle." He rolled his eyes when her jaw dropped again. "This is getting tiresome so I must be off. I shall speak with you tomorrow, Miss Andrews."

Sarah could clearly see the amusement in his eyes. _He was laughing at her! What an absolute prick!_

"Until tomorrow, Miss Andrews." He bowed low before turning on his heel and sauntering off down the corridor, twirling his wand in his fingers as he went.

After a moment of silence, Hollie moved forward and gave Sarah a reassuring pat on the shoulder.

"And now you've properly met Tom Riddle." She sighed. "Come on, let's go to bed, I'm seriously tired."

Sarah nodded wordlessly and began walking towards the Ravenclaw tower.

Well, there was one thing she was definitely positive of.

If anything, this year was going to be _far_ from boring.

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_There you go! Reviews please! Thanks. _


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